He is the only British man guaranteed to be on the start line alongside Usain Bolt, Yohan Blake, Justin Gatlin and the rest for the 100m Olympics final.

Not Dwain Chambers, the veteran sprinter once banned for taking drugs who thought his chance of appearing at a Games had gone. Nor Adam Gemili, the 18-year-old world junior champion who has sprung from nowhere to seize a spot on the British team.

The man who knows he will be there is the London 2012 chief starter, an unassuming 61-year-old from County Durham. Alan Bell will also be the only man welcomed into the Olympic Park with open arms who will be carrying a pistol.

Bolt, the Jamaican looking to make Olympic history but no longer regarded as a sure thing in the 100m and 200m, could be forgiven for never wanting to see Bell again.

Bell fired the gun when Bolt false-started in the 100m final at the world championships in Daegu, South Korea, last year.

But Bell did not even realise it was the most famous athlete in the world Bolt who he had disqualified, so focused was he on the task in hand.

"You call a false start and it's not until afterwards you realise who it is, you're just concentrating on lane five.

"You look at it and by the time you have a conversation with the recall starter and look at the printouts from the starter equipment, Bolt already had his vest off and was ready to walk," he said.

"The issue then was preserving his integrity, getting him away from the media melee, and settling down the other seven guys who now had a chance at a gold medal."

Bell remembers that he left the track to meet his partner Lesley and was confronted with Bolt's mother. "My first thought was she was bound to be disappointed and to let her have a pop.

"But she was brilliant. She said he would learn from his mistake and come back for the 200m. And, boy, did he." Bolt took the gold at the longer distance.

"I passed him in the warm-up area for the relay. He just smiled and it was history. He's a strong character, an exceptional athlete and a pretty good human being. He's one of the best things to ever happen to the sport."

However, he agrees with the controversial "one strike and you're out" disqualification rule that caught Bolt out. "A false start is a rarity now.

"The real challenge has been for the starters to hold their nerve. The good ones hold their concentration for that fraction longer. It's very easy to say 'set' and fire the gun immediately and rid yourself of the obligation."

He says a good starter needs composure and a sense of judgment. "I've got arguably as good a concentration span over 30 seconds as anyone else in the world. The rest of the time I'm happy go lucky, I'm smiling and enjoying myself. But that focus is so important."

Bell is a former high jumper who had a serious injury in 1976 and was told he could never jump again. Wanting to stay involved, he became an official at his local athletics club. He loved it immediately, he said.

As Gateshead took off as a major athletics venue in the late 1970s Bell, a longstanding friend of distance runner turned Great North Run founder Brendan Foster, worked his way up the officiating ladder. "I got exposed to the big time environment and got the bug for it."

Bell, who works with the Youth Sport Trust to try to inspire young people to become officials, said: "One of the huge challenges is not only starting races of huge significance with the eyes of the world on you, but the range of athletes who will be there. In the 100m you'll have the Bolts and the Gays. But you'll also have people who are from not such advanced countries athletically, but for whom it's also the biggest moment of their lives."

At the 2011 world championships, he came across one athlete who had never used starting blocks before. Another, he says, habitually "backs into the blocks like a crab". Bell's task is to read the idiosyncrasies of each and get the race off as smoothly as possible.

Chambers may remember Bell too. The first big event Bell remembers firing the gun at was the Euro Youth Olympics in Bath, when Chambers won the 100m as a 16-year-old.

Bell will lead a team of starters in London, all of whom he knows well. "Technically we'll be bloody good. Socially, we'll have a ball," he says. Bell does not get paid for his time but says his 35 years as an official have given him experiences money can not buy.

"I've probably been to more places as an official than any international athlete running in the UK. I've got a collection of medals from major events that is irreplaceable for me. Sport in this country relies on volunteers."

He is a reminder that, for all the rewards and commercialism of sport at the elite end, the grassroots are only sustained by a huge army of volunteer coaches and officials.

He might be assiduously fair when starting a race, but once the athletes have set off Bell says he will be screaming at Mo Farah with the other 80,000 people packed into the Olympic Stadium.

"I want a Brit with a gold medal around his neck. There's no favouritism when I've got a gun in my hand, but when I'm there spectating in the middle, I'm a Brit. I'll never forget that."

And he shakes his head as he considers the scale of the task ahead. "I have the good fortune to be alive when the Olympic Games is in my country. To be able to play a part in my sport, in my country, for my own people – the privilege is off the scale. It doesn't get any better."